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Astronomers using ESO telescopes and others around the world have found three new planets orbiting stars in a cluster called Messier 67.
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Only a handful of such planets in clusters were known up to now.
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And, surprisingly, one of the newly found planetary host stars seems to be an almost perfect solar twin
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— a star that is essentially identical to our own Sun.
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It’s the first exoplanet orbiting a solar twin in a star cluster to be discovered.
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This is the ESOcast! Cutting-edge science and life behind the scenes of ESO, the European Southern Observatory.
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Exploring the ultimate frontier with our host Dr J, a.k.a. Dr Joe Liske.
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Good news everyone! 3 brand new exoplanets have been discovered.
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Considering that we already know about a thousand exoplanets, that might not sound like much
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but this finding is in fact, a little unusual because these 3 planets orbit stars inside a cluster of stars known as Messier 67.
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These recent discoveries confirm that planets in clusters are quite common — although very hard to spot.
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They will also allow scientists to examine how planets form in the crowded environment of a star cluster.
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To find the new exoplanets, astronomers used the HARPS instrument on the 3.6-metre telescope at ESO’s La Silla Observatory.
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They carefully monitored 88 selected stars in Messier 67 for a number of years.
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That allowed them to look for the tiny tell-tale motions of the stars that reveal the presence of orbiting planets.
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Three planets were discovered in the cluster.
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Two of these planets orbit stars similar to the Sun,
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and one orbits a more massive and evolved red giant star.
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The first two planets both have about one third the mass of Jupiter and orbit their host stars in seven and five days respectively.
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The third planet takes 122 days to orbit its host and is more massive than Jupiter.
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The host star of one of the planets turned out to be a remarkable object
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— it’s one of the best solar twins ever identified.
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The star is almost identical to the Sun in terms of its mass, age, chemical composition and other characteristics.
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Also, it’s the first solar twin in a cluster that has been found to host a planet.
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Solar twins, solar analogues and solar-type stars are categories of stars based on how similar they are to our own Sun.
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Solar twins — stars almost identical to the Sun — are very rare,
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but the other classes, where the similarity is a lot less precise, are much more common.
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Astronomers had not found many planets around cluster stars in the past, but now they are finally showing up.
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The new results from the HARPS instrument show that planets in open star clusters
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are probably about as common as they are around isolated stars
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...so that’s a lot of planets!
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This is Dr. J signing off for the ESOcast.
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Join me again next time for another cosmic adventure.
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Transcription by ESO; translation by -